The present invention relates to a visual inspection apparatus for tablets comprising the right side inspection drum for holding tablets on the outer peripheral surface and being rotated at fixed speeds to thereby carry the tablets, the wrong side inspection drum for receiving the tablets from the right side inspection drum to hold the tablets on the outer peripheral surface in the inverted state and being rotated at fixed speeds to thereby carry the tablets, and the right side imaging device and the wrong side imaging device for photographing the tablets carried while being held by the right side inspection drum and the wrong side inspection drum to take the right side images and the wrong side images of the tablets, the apparatus inspecting the rejected appearance of the right side and the wrong side of the tablets from the obtained right side image and the wrong side image.
In the past, the visual inspection for inspecting whether adhesion of foreign matter on tablets, contamination and deformation such as break and crack, or defects such as rejected print occur or not is automatically carried out using a visual inspection apparatus. In the case where flat-shaped tablets are automatically inspected using such a visual inspection apparatus as described, there is normally employed a method for processing images obtained by photographing tablets with a camera during carriage to thereby detect the defects. In the case of the flat-shaped tablets, it is necessary to photograph them from three different angles, i.e. the side (peripheral edge), the right side and the wrong side for inspection. To this end, it is necessary to control the attitude of tablets accurately in order to positively photograph the places to be inspected, and necessary to change, during carriage, the attitude of tablets according to three photographing places, i.e. the side (peripheral edge), the right side and the wrong side.
As such a visual inspection apparatus for tablets, an inspection apparatus shown in FIG. 11 can be specifically illustrated.
This visual inspection apparatus comprises a tablet supply section 1 for supplying a number of flat-shaped tablets (hereinafter referred to as tablets) stored in a hopper 11 to an inspection mechanism section, a side inspection section 2 comprising a side inspection drum 21 and a side imaging device 22, an attitude conversion section 3 having an attitude conversion drum 31, a both-side (the right and the wrong side) inspection section 4 having the right side inspection drum 41, the wrong side inspection drum 42, the right side imaging device 43 and the wrong side imaging device 44, a classification section 5 having a classification drum 51, an excellent article recovering conveyor 52 and a rejected article recovering can 53, and a decision section for processing images obtained from the three imaging devices 22, 43 and 44 to detect the presence or absence of the rejected appearance though not shown. In the figure, reference numerals 221, 431 and 441 designate cameras, and numerals 222,432 and 442 designate illumination devices.
The visual inspection by the above-described visual inspection apparatus is carried out in the following procedures:
(1) A number of tablets supplied at random from the hopper 11 are continuously supplied to the side inspection drum 21 of the side inspection section 2 in a upright state with a diametrical direction vertically set by the tablet supply section 1 (hereinafter referred merely to as "upright state");
(2) the tablets are stored in the upright state into a holding pocket of the side inspection drum 21, the tablets are carried downward by the rotation of the drum 21, and the tablets are photographed by the right side imaging device 22 while rotating the tablets being carried within the holding pocket to obtain the image of the whole side of the tablets; PA1 (3) the tablets are transferred to the attitude conversion drum 31 of the attitude conversion section 3, the tablets in the upright state are laid down laterally by the drum 31 into a prostrated state with the thickness direction vertically set (hereinafter merely referred to as "prostrated state"), after which the tablets are delivered to the right side inspection drum 41 of the both-side inspection section 4; PA1 (4) the tablets are stored in the prostrated state into a tablet storing pocket formed on the surface of the right side inspection drum 41, the tablets are carried downward by the rotation of the drum 41, and the tablets being carried are photographed by the imaging device 43 to obtain the right side images of the tablets; PA1 (5) the tablets are delivered to the wrong side inspection drum 42 and stored in the inverted prostrated state into the tablet storing pocket of the wrong side inspection drum 42, the tablets are carried downward by the rotation of the drum 42, and the tablets being carried are photographed by the imaging device 44 to obtain the wrong side images of the tablets; and PA1 (6) then, the tablets are transferred to the classification drum 51 of the classification section 5, the rejected tablets are transferred to the rejected article recovering can 53 according to the inspection results obtained by processing the side images, the right side images and the wrong side images, and the excellent tablets are transferred onto the excellent article recovering conveyor 52 and carried to the recovering conveyor c for recovery.
However, in the above-described visual inspection apparatus, the tablets being held on the outer peripheral surfaces of the right side inspection drum 41 and the wrong side inspection drum 42 are so unstable that the images are sometimes not always taken stably, and in addition, when the tablets are delivered between the right side inspection drum 41 and the wrong side inspection drum 42, damages such as crack or break sometimes occur.
More specifically, in both the above-described right side inspection drum 41 and the wrong side inspection drum 42, tablets t are stored in tablet storing pockets 411, 421 provided in the outer peripheral surfaces of the drums 41, 42, and the tablets t are held within the pockets 411, 421 by suction of suction holes 412, 422, as shown in FIG. 12. In this case, the pockets 411, 421 are formed to be slightly larger than the tablets t in order to smoothly effect the delivery of the tablets t. Therefore, the tablets t stored in these pockets 411, 421 sometimes cause shakes within the pockets 411, 412. Eventually, it is sometimes not possible to obtain good images. Further, since the tablets are photographed in the state that they are stored in the recessed pockets 411, 421, shade tends to occur on the tablets during the photographing, by which obtaining the good images is sometimes blocked.
Further, the tablets t are delivered from the right side inspection drum 41 to the wrong side inspection drum 42 by pressure air jetted from a suction hole 412, when the pockets 411 of the right side inspection drum 41 are registered with the pockets 421 of the wrong side inspection drum 42, to extrude the tablets t from the pockets 411 of the right side inspection drum 41. Thus, the tablets t are attracted into the pockets 421 of the wrong side inspection drum 42 to move. At that time, when the tablets t move between both the drums 41 and 42 formed of metal such as stainless steel, a great load or shock is applied to the tablets t so that damages such as crack or break sometimes occur in the tablets t.
Furthermore, it is necessary to set the tablet storing pockets 411, 421 of the right side inspection drum 41 and the wrong side inspection drum 42 to proper size according to the size and shape of the tablets t in order to smoothly effect the delivery of the tablets t, and to stably locate them without shake for carriage. Therefore, when the kind (size and thickness) of the tablets subjected to inspection is changed, the right side inspection drum 41 and the wrong side inspection drum 42 need to be replaced with those having the tablet storing pockets 411, 421 of proper size on all such occasions. When the tablets to be inspected are changed, extremely cumbersome operation is necessary.